Ball screw/nut type linear actuators comprising a ball screw/ nut mechanism and a motor are known as one type of linear actuator.
FIG. 2 is a schematic vertical cross-sectional view showing a typical ball screw/nut type linear actuator. In the ball screw/nut type linear actuator 100 as shown in the drawing, a ball screw shaft 102 is connected and fixed to a motor shaft 101 in a coaxial state, a ball nut 103 which is screwed onto a ball screw shaft 102 is held in a non-rotating state, and the rotating of the ball screw shaft 102 rotates causes the ball nut 103, which is connected to a load, to move in a forward-backward direction along the ball screw shaft 102.
It is usual for the motor shaft 101 and the ball screw shaft 102 to be connected and fixed via a coupling 104. Accordingly, a motor 105, the coupling 104, the ball screw shaft 102, and a ball screw shaft support bearing 106 are serially arranged in the direction of the shaft line. Consequently, conventional ball screw/nut type linear actuators 100 have problems that they have a long shaft length and are heavy due to need to have the coupling 104, support bearing 106, and other components.